JPH03181001A - Rotary head type recorder - Google Patents

Abstract

PURPOSE:To reduce the degradation in picture quality due to dubbing by generating a clock signal synchronized with a rotation phase signal and reading out an information signal, which is stored in a storage means and should be recorded, synchronously with this clock signal to supply it to a rotary head. CONSTITUTION:A tack pulse detecting circuit 27 has a coil which detects the magnetic flux from a magnet 25 to generate the rotation phase signal indicating the rotation phase of rotary heads 21 to 24. The tack pulse is inputted to a phase synchronizing circuit 30. That is, the tack pulse is used as a reference input signal and has the phase compared with that of the output signal of a VCO 33 by a phase comparator 31, and the phase comparison result is supplied as a control voltage to the VCO 33 through an LPF 32 to control the oscillation frequency of the VCO 33, and thereby, the clock signal synchronized with the tack pulse is generated from the VCO 33 and is read out and is supplied as a read clock to a read control circuit 10. Thus, a reproduced picture of less jitter is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a rotary head type recording device used for recording information signals such as video signals, and particularly to a rotary head type recording device used for recording information signals such as video signals. The present invention relates to a rotary head type recording device that records on tape.

(Prior Art) A typical example of a rotary head type recording device is a helical scan type VTR. In an NTSC VTR, one field of video signals is recorded on one helical track.

On the other hand, in VTRs for high-definition television signals, which are currently being actively developed, the amount of information recorded on the tape is much larger than in the case of the NTSC system, so the amount of information recorded in one field is A multi-track method is used in which the signal is divided into multiple helical tracks and recorded. Therefore, during recording, the input video signal is converted into a digital signal by an A/D converter and then multiplexed.
For example, only one frame is written to the memory, and after one frame, a reference signal of a constant frequency (for example, 30 Hz) is used to write the data to the memory.
After being read out frame by frame, it is converted back into an analog signal by a D/A converter and distributed to a plurality of rotary heads via a recording amplifier. As a result, the signal of one field is divided into, for example, six tracks and recorded on the tape.

The rotating head is attached to the rotating drum, and the drum motor that drives the rotating drum is controlled by a drum servo circuit so that the phase difference between the tack pulse, which indicates the rotational phase of the rotating drum, and a reference signal is a predetermined constant value. be done. In this case, the rotational speed of the rotating drum actually fluctuates due to fluctuations in load torque, fluctuations in the drum servo circuit system, etc. (see FIG. 3).

If there is such a variation in the rotational speed of the rotating drum, the track length on the tape will vary because the video signal is read from the memory using a reference signal of a constant frequency. In other words, one track of the video signal read from memory is a fixed time length (for example, 1/6 field), whereas the time it takes for the rotary head to rotate and scan the tape during this time length is The track length fluctuates because it fluctuates due to fluctuations in the rotational speed of the drum.

If the track length on the tape changes, jitter will appear in the reproduced image when playing back the video signal recorded on the tape.
The advantage of the high picture quality of the high-definition television system is lost.

Furthermore, when editing by dubbing from tape to tape using a plurality of VTRs, the number of times of dubbing is limited because the amount of change in recording position increases each time dubbing is performed, resulting in increased deterioration of image quality. This becomes a big problem in business VTRs that require dubbing and editing many times.

(Problems to be Solved by the Invention) As mentioned above, the rotary head type VTR, like the conventional multi-track VTR, once writes information signals into a memory, reads them out using a reference signal of a constant frequency, and records them on a tape using a rotary head. In recording devices, the track length and recording position on the tape fluctuate due to fluctuations in the rotational speed of the rotating drum to which the rotary head is attached, resulting in increased jitter in the reproduced image and significant deterioration in image quality due to dubbing. there were.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a rotary head type recording device that can eliminate fluctuations in track length and recording position on a tape due to fluctuations in the rotational speed of a rotary drum.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention generates a rotational phase signal indicating the rotational phase of a rotary head using a clock generation means configured using a phase synchronization circuit or the like. A clock signal synchronized with is generated, and the information signal to be recorded stored in the storage means is read out in synchronization with this clock signal and supplied to the rotary head.

(Function) In the present invention, since the information signal read from the storage means and recorded on the tape is synchronized with the rotational phase signal, it is also synchronized with fluctuations in the rotational speed of the rotating drum.

Therefore, the time length of the information signal recorded on each track on the tape changes depending on the rotation speed, such that the faster the rotation speed of the rotating drum becomes, the shorter it becomes, and the slower it becomes, the longer it becomes. The recording position is kept constant.

This reduces jitter in reproduced images caused by variations in track length, and even during dubbing, there is little variation in the recording position from tape to tape, so signal quality is maintained at a good level.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram in which the present invention is applied to a VTR for high-definition television signals as an embodiment of the rotary head type recording device of the present invention. However, since the present invention is characterized by a recording apparatus, only the recording circuit system is shown in FIG. Further, FIG. 2 shows a timing diagram of each part of FIG. 1.

In Fig. 1, three input terminals 1, 2.3 have a second
R in the high-definition television video signal shown in Figure (a)
(red), G (green), and blue (B) color signals are input. These R,G.

Each B signal is converted into a digital signal by an A/D converter 4.5.6, and then becomes a multiplexed video signal by a multiplexer 7, which is manually input to a digital memory 8.

The digital memory 8 is supplied with a write clock from a write control circuit 9 and a read clock from a read control circuit 10 . That is, the digital video signal from the multiplexer 7 is once stored in the digital memory 8, for example.
The data is written one frame at a time and read out from the digital memory 8 frame by frame.

Digital video signals A and B are output from the digital memory 8.
The data is read out separately into two channels.

These A and B channel digital video signals are D/A
After being converted back to an analog signal by a converter 11.12, it is sent to recording amplifiers 13, 14, and then to a head selector switch 15.1.
6 to the rad assembly 17 for rotation. The head changeover switches 15 and 16 are activated by the head changeover signal shown in FIG. 2(d), which is generated from the drum servo circuit 28 after a certain time T1 from the tack pulse (described later) shown in FIG. 2(C). As shown in FIG. 5, the rotary head assembly 17, which alternately switches between the A2/B2 side and the A2/B2 side, has an upper rotary drum 18 and a lower rotary drum 19 disposed coaxially, and a drum attached to the upper rotary drum 18. motor 20
are connected, and multiple pieces (four pieces in this example) are connected to the rotating drum 18.
The rotary head 21, 22, 23, 24 and a tack pulse detection magnet 25 are attached.

The tack pulse detector 27 has a coil that detects the magnetic flux from the magnet 25, and generates a tack pulse shown in FIG. 2(C), that is, a rotational phase signal indicating the rotational phase of the rotary heads 21 to 24.

A magnetic tape 26 is wound around the drum 1819, and one field of video signals is divided into six tracks and recorded on this tape 26 by the rotary heads 21 to 24, as shown in FIG. In the case of high-definition television signals, one frame has, for example, 1125 lines, but the effective lines (period excluding the vertical blanking period) are 103 lines.
Assuming 6 lines, the number of lines in one field is 518 lines, so the number of lines recorded on one track on the tape 26 is 5187B = 86.33, and video signals of 87 lines or less are recorded on one track. Ru.

The drum servo circuit 28 receives tack pulses from the tack pulse detector 27 and input from a terminal 29 as shown in FIG.
), i.e., a frame frequency (e.g., 30 Hz), and in order to match the phase of both signals, the phase of the tack pulse is always kept within a certain period of time with respect to the reference signal, as shown in Fig. 2. T. to be late,
The rotational speed of the drum motor 20 (the rotational speed of the upper rotating drum 18) is controlled.

On the other hand, the tack pulse is also input to a phase locked circuit (hereinafter referred to as a PLL circuit) 30. This PLL circuit 30 is composed of a phase comparator 31, a low pass filter (LPF) 32, and a voltage controlled oscillator (VCO). That is,
By using the tack pulse as a reference input signal, comparing the phases of this and the output signal of the VC033 with the phase comparator 31, and supplying the result of the phase comparison as a control voltage to the VC033 via the LPF 32 to control the oscillation frequency of the VC033,
A clock signal synchronized with the tack pulse is generated from the VC033.

This clock signal is supplied to the read control circuit 10 as a read clock.

Next, the operation of this embodiment will be explained. Read control circuit 10
Each time a tack pulse is input from the tack pulse detector 27, the readout start address of the digital memory 8 is set at a time T2 after the tack pulse is input. The read control circuit 10 increments the read address of the memory 8 by one each time one clock signal is input from the PLL circuit 30.

As a result, the digital video signals of channels A and B are read out from the digital memory 8. The read digital video signals of both channels A and B are sent to the D/A converter 11.
12, it is converted back to an analog signal by recording amplifier 13.1.
After being amplified by 4, the head changeover switch 15.16
The signal is supplied to the rotary heads 21 to 24 via the above, and recorded on the tape 26.

Rotating drum] 8 rotational speed (i.e. drum motor 20
(rotational speed) is controlled by a drum servo circuit 28. In this case, when the rotational speed of the rotating drum 18 fluctuates, the phase of the tack pulse fluctuates. Due to this phase variation of the tack pulse, the frequency of the read clock supplied to the read control circuit 10 also changes accordingly. This situation is shown in FIG.

As shown in FIG. 3, when the rotational speed of the rotary drum 18 rises above the standard, the oscillation frequency of the VC033 in the PLL circuit 30 becomes high, and the frequency of the read clock becomes high. As a result, the time length of the video signal read from the memory 18 becomes shorter. Furthermore, when the rotational speed of the rotary drum 18 falls below the standard, the oscillation frequency of the VC033 becomes low, and the frequency of the read clock signal becomes low. This increases the time length of the video signal read from memory 18. That is, the time length of the video signal recorded on each track on the tape 26 changes depending on the rotation speed, such that the faster the rotation speed of the rotary drum 18, the shorter it becomes, and the slower the rotation speed of the rotary drum 18, the longer it becomes.

In this way, the video signal is read out from the digital memory 8 in synchronization with the phase of the tack pulse, that is, with the rotational speed fluctuation of the rotating drum 18, and the time length of the video signal changes in accordance with this rotational speed fluctuation. . Therefore, the track length on the tape 26 is kept constant despite variations in the rotational speed of the rotary drum 18, and the video signal is always recorded at a predetermined position on the tape 26 as a track of a predetermined length. As a result, when the video signal recorded on the tape 26 is reproduced, a reproduced image with less jitter can be obtained. Furthermore, since the recording position of the video signal on each track on the tape 26 is kept constant, there is little deterioration in image quality even when dubbing editing is repeated many times.

In addition, in the above embodiment, there is a
The magnets 25 for generating tack pulses are provided to generate only one tack pulse per one rotation of the rotating drum 18. If two tack pulses are generated during this period, more accurate rotational phase signal information can be obtained. Therefore, the above-mentioned effects by controlling the read clock of the memory 8 using the rotational phase signal can be further enhanced.

[Effects of the Invention] According to the present invention, by reading information signals from a memory for temporarily storing them using a clock signal synchronized with a rotational phase signal indicating the rotational phase of the rotating head, the rotating drum can be read out. By reading out information signals in synchronization with rotational speed fluctuations and recording them on the tape using a rotary head, it is possible to reduce fluctuations in track length and recording position on the tape.

Therefore, jitter during reproduction is reduced, and signal deterioration due to dubbing can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a rotary head type recording device according to an embodiment of the present invention, FIG. 2 is a timing diagram showing the recording operation of the same embodiment, and FIG. Figure 4 shows the recording pattern on the tape using the multi-track system, and Figure 5 shows the schematic structure and rotation of the rotating drum assembly in the same example. FIG. 3 is a diagram showing the arrangement of heads. 8... Digital memory (storage means) 17... Rotating head assembly 18... Rotating drums 21-24... Rotating head 26... Tape 27... Tack pulse detector (rotational phase signal generating means) ) 28...Two drum servo circuits...Reference signal input terminal 30...Phase synchronization circuit 1...Phase comparator 2...Low pass filter 3...Voltage controlled oscillator

Claims (2)

[Claims] (1) A rotary head type recording device that records information signals on a tape using a rotary head assembly having a rotary drum, a rotary head mounted thereon, and means for generating a rotational phase signal indicating the rotational phase of the rotary head. , storage means for temporarily storing an information signal to be recorded; clock generation means for generating a clock signal synchronized with the rotational phase signal; and reading of the information signal stored in the storage means in synchronization with the clock signal. A rotary head type recording device comprising: means for outputting the information signal; and means for supplying the information signal read from the storage means by the means to the rotary head. (2) The clock generation means uses the rotational phase signal as a reference input signal, compares the phases of this reference input signal and the output signal of the voltage controlled oscillator, and based on the result of the phase comparison, the oscillation frequency of the voltage controlled oscillator. 2. The rotary head type recording apparatus according to claim 1, further comprising a phase synchronization circuit that generates a clock signal synchronized with the rotational phase signal from the voltage controlled oscillator by controlling the rotational phase signal.